This invention relates to a water-purifying apparatus, which is especially adapted to reduce the radon content of radon-contaminated water and which comprises a reactor tank for treating the radon-contaminated water, a radon-releasing means arranged in the reactor tank to receive and treat water from a first pump adapted to supply water from a source of water containing radon-contaminated water, the water from the radon-releasing means accumulating in the reactor tank, an inlet duct extending between the first pump and the radon-releasing means, an outlet duct from the reactor tank, said outlet duct being connected to a water consumption system, and a radon-gas outlet from the reactor tank.
U.S. Pat. No. 4,371,383 teaches a radon-removal system intended to be arranged between a source of water and a pressure storage tank. According to the US specification, this system succeeds in removing 80-90% of the radon by aerating the water, but nevertheless does not possess the efficiency required to achieve results below the Swedish maximum permissible value of 500 Bq/l, if the contaminated water has a radon content of 5000 Bq/l or more.
SE 464,712 discloses a water-purifying apparatus which effectively removes, inter alia, iron and manganese from water. The Swedish technique is based on effective aeration of the water, a technique that has proved to be useful also when it comes to removing radon. However, radon-contaminated wells are often fairly deep (70-100 m), which means that the amount of water lifted is rather small, for instance 5 l/min. A much greater flow rate of at least 25 l/min is required for effective aeration of the water. When the flow rate is too small, the aeration is less effective, which of course has an adverse effect on the removal of radon.